basis of record Bouillon, J.; Boero, F. (2000). Synopsis of the families and genera of the Hydromedusae of the world, with a list of the worldwide species. Thalassia Salent. 24: 47-296 (look up in IMIS) [details]

Diagnosis Colony forming upright pinnate shoots, mono- or polysiphonic, branched or unbranched, arising from creeping hydrorhiza or from anchoring filaments; hydrocladia alternate or opposite in one plane, or arranged spirally; hydrothecae uniseriate, usually completely adnate, with or without marginal cusps, with or without intrathecal septum, absent from hydrocaulus except in basalmost segment; nematophores with nematothecae, not as naked sarcostyles; nematothecae at least partially fused to hydrothecae, one-chambered (monothalamic) and immovable; hydrotheca typically flanked with one pair of lateral nematothecae, and with an unpaired median inferior nematotheca that may be doubled or have two terminal apertures; sometimes also a pair of superior nematothecae; gonothecae lacking nematothecae, unprotected, or surrounded by curved branches in phylactocarp, or nearly completely enclosed within corbulae; fixed sporosacs or swimming gonophores. [details]